Field of the Invention
The present invention generally relates to a sewer overflow discharge monitoring system. More specifically, it relates to systems and methods using levels and tilt measurements to monitor sewer overflow discharges from structures protected with tidal or river inflow flap gates
Discussion of the Background
In many cities wastewater and rainwater are collected together in a combined sewer system. To prevent localized flooding in basements and streets during a heavy rain event, these combined waters are usually diverted into a local river or stream, thereby creating a combined sewer overflow (CSO) event.
Because these waters are highly impacted with chemical and biological contaminants, CSO events pose a major public health hazard. The United States Environmental Protection Agency (USEPA) issues all wastewater utilities in the United States a National Pollutant Discharge Elimination System (NPDES) permit. This permit typically requires a utility to report the occurrence, timing, and estimated volume of CSO discharges in a regular basis.
The report, called a Discharge Monitoring Report (DMR), increasingly requires electronic real-time data from the sewer system be sent to the utility. The NPDES permit typically also requires that the utility provide near real-time public notification of CSO events to reduce the possibility of human contact with untreated wastewater in recreational waters.
Conventional CSO structures are composed of a regulator, such as a weir, that diverts wastewater to a pipe, referred to as a CSO pipe, which acts as a relief point to the sewer system. The CSO pipe typically conveys the excess wastewater to a water body such as a river, lake, or the sea.
In certain instances the CSO structure can be influenced by the water body into which the CSO discharges. In these situations it is customary to use a flap gate to prevent river, lake or sea water from entering the sewer system. Monitoring these kinds of CSO structures is challenging. For example, some of these water bodies may experience high tide. During a high tide CSO event, significant turbulence in the CSO structure can preclude the use of certain meters. One example is area-velocity flow meters typically used to quantify CSO incidents. In addition, wave action in the receiving water body can generate oscillations on the flap gate in the CSO structure. It would be desirable to have a CSO structure that addresses these issues and concerns that arise with conventional CSO structures, particularly with respect to the effects of the external water body.